For more than half a century, a massive, oil-fired plant has been churning out electricity from an island in the heart of Maine’s Casco Bay, where sailors use its towering smokestack for navigation.

The old generator is expensive to run and dirtier than new technologies, so these days it comes on only a few times a year. Nonetheless, since December, the wires on the island have been humming pretty much nonstop.

“It’s the 60 hertz hum, we engineers call. It’s the sound we like to hear ‘cause we know we’re running,” says Jeff Plew, project manager for NextEra, a national electricity company that focuses on renewable energy.

Here, in the shadow of the old fossil-fuel plant, Plew led the development of New England’s biggest-yet battery. Giant batteries are starting to make a mark on the electricity grid that serves all of New England — the unique characteristics of which could supercharge solar and wind energy development in the region.

He says grid-scale batteries can serve many functions. The setup here helps stabilize the frequency of the electricity that flows through the regional grid, at that 60 hertz, or cycles per second.

“We’ll go into the battery room now,” Plew says.

The battery room — a former warehouse — holds eight concrete blocks as big as cargo containers, housing a total of 1,300 individual lithium-ion batteries, each about the size of a desk computer. They throw off some heat.

“Just like your phone, you can kind of feel it getting hot. We have cooling systems in place just to maintain the equipment at their optimal operating parameters,” Plew says.

Every four seconds, computers at grid operator ISO New England’s Holyoke, Massachusetts, headquarters tell the batteries here whether to pull in energy and store it, or to discharge it back onto the grid. It helps to balance the inevitable mismatch that occurs between the amount of energy generators are pushing onto the grid at any given moment and the amount that customers are taking from the grid.

It can be much more efficient to ask energy storage systems like this to fine-tune the grid’s frequency than, say, to try to toggle a big natural gas plant’s output up and down.

“It’s just on a much faster ramp than you’d see with a typical generator. A typical generator might ramp at a rate of 1-10 megawatts maybe per minute. This battery can do that full range in a second or less,” Plew says.

Ideally, NextEra can provide the service at a price that reduces costs for consumers and still make a profit. And this is really just the beginning.

Battery technology is advancing quickly, partly thanks to the rise of electric vehicles, and costs are coming down. Stephen Rourke, a senior system planner at ISO New England, says they’ve really just started studying the technology.

“I would say it’s just been really in the last year or so that we’ve had a grid-scale battery in our study queue at all. In fact the Casco Bay project up in Maine was the first to go through our study process,” he says.

It won’t be the last: There are now eight more such projects seeking study and approval by ISO New England. And a lot is happening on a smaller scale, too.

On a former landfill in Rutland, Vermont, utility Green Mountain Power has paired a battery array with a solar array. Project manager Josh Castonguay says the batteries can reduce the burden on the regional grid on high-demand days by delivering stored-up solar electricity directly to local consumers.

One hot summer day last year, that “peak-shaving,” as it’s called, saved GMP customers some real money.

“We discharged the batteries right at that right hour, lowered our demand overall and just that one hour saved our customers $200,000 in capacity costs,” Castonguay says.

On top of that, GMP’s batteries solve a vexing renewable energy challenge: how to handle surges and drop-offs in the bulk electricity that wind and solar plants deliver, depending on whether the wind is blowing or the sun is shining. Batteries can soak up excess energy when it’s being produced, and then push it onto the grid when the generators go silent.

The batteries’ “firming” and “smoothing” abilities allow energy produced by intermittent resources to match up with real-time system needs, 24/7. Plew says they will be a significant driver for the next wave of wind and solar development.

“It gives you the same ability essentially as what you get from a traditional generator. It is the Holy Grail for renewables,” he says.

NextEra, for one, is grabbing the grail with both hands. It has proposed to pair batteries even bigger than the Casco Bay array with wind turbines and solar generators in western Maine. And that’s just one of several such projects that are being proposed around New England, as state and regional climate policies seek to inject ever more renewable energy into the mix.

Related Content

The nine-state Regional Greenhouse Gas Initiative consortium has settled on a proposed update to the cap-and-trade program that would call for a 30 percent reduction in carbon pollution from the region's power plants by 2030.

A play by Massachusetts to inject more renewable power into its electricity mix could reshape the entire region's energy landscape. Dozens of developers are competing to offer Massachusetts the best price for long-term contracts to supply clean energy to hundreds of thousands of homes.

But many of the projects also face another challenge: convincing residents of Northern New England it's in their interest to host the Bay State's extension cord.